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Todd Lipcon commented on HDFS-744:
----------------------------------
Looks pretty good! Just a few small things:
- looks like hard tabs still snuck in one spot
- I don't think hsync() needs to be synchronized: ie further writes could proceed to the stream
while an earlier writer is waiting on a sync response
----
{code}
// repeated hsyncs, not avoiding unnecessary sync here
out.hsync();
checkSyncMetric(cluster, 2);
{code}
maybe add a note that says more explicitly something like: this is a potential future optimization
that is not yet implemented, or something?
> Support hsync in HDFS
> ---------------------
>
> Key: HDFS-744
> URL: https://issues.apache.org/jira/browse/HDFS-744
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: data-node, hdfs client
> Reporter: Hairong Kuang
> Assignee: Lars Hofhansl
> Attachments: HDFS-744-trunk-v2.patch, HDFS-744-trunk-v3.patch, HDFS-744-trunk-v4.patch,
HDFS-744-trunk-v5.patch, HDFS-744-trunk-v6.patch, HDFS-744-trunk-v7.patch, HDFS-744-trunk.patch,
hdfs-744-v2.txt, hdfs-744-v3.txt, hdfs-744.txt
>
>
> HDFS-731 implements hsync by default as hflush. As descriibed in HADOOP-6313, the real
expected semantics should be "flushes out to all replicas and all replicas have done posix
fsync equivalent - ie the OS has flushed it to the disk device (but the disk may have it in
its cache)." This jira aims to implement the expected behaviour.
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